.\"-
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.\" Copyright (c) 2018 Kyle Evans <kevans@FreeBSD.org>
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.Dd February 25, 2018
.Dt STYLE.LUA 9
.Os
.Sh NAME
.Nm style.lua
.Nd
.Fx
lua file style guide
.Sh DESCRIPTION
This file specifies the preferred style for lua source files in the
.Fx
source tree.
Many of the style rules are implicit in the examples.
Be careful to check the examples before assuming that
.Nm
is silent on an issue.
.Pp
The copyright header should be a series of single-line comments.
Use the single-line comment style for every line in a multi-line comment.
.Pp
After any copyright header there is a blank line.
.Pp
The preferred method of including other files and modules is with
.Fn require name ,
such as:
.Bd -literal
-- License block

config = require("config");
menu = require("menu");
password = require("password");
-- One blank line following the module require block
.Ed
.Pp
.Fn include
is generally avoided.
.Pp
Indentation and wrapping should match the guidelines provided by
.Xr style 9 .
Do note that it is ok to wrap much earlier than 80 columns if readability would
otherwise suffer.
.Pp
Where possible,
.Fn s:method ...
is preferred to
.Fn method s ... .
This is applicable to objects with methods.
String are a commonly-used example of objects with methods.
.Pp
Testing for
.Va nil
should be done explicitly, rather than as a boolean expression.
Single-line conditional statements and loops should be avoided.
.Pp
.Ic local
variables should be preferred to global variables in module scope.
internal_underscores tend to be preferred for variable identifiers, while
camelCase tends to be preferred for function identifiers.
.Pp
If a table definition spans multiple lines, then the final value in the table
should include the optional terminating comma.
For example:
.Bd -literal
-- No terminating comma needed for trivial table definitions
local trivial_table = {1, 2, 3, 4}

local complex_table = {
	{
		id = "foo",
		func = foo_function, -- Trailing comma preferred
	},
	{
		id = "bar",
		func = bar_function,
	},	-- Trailing comma preferred
}
.Ed
.Pp
This reduces the chance for errors to be introduced when modifying more complex
tables.
.Pp
Multiple local variables should not be declared
.Sy and
initialized on a single line.
Lines containing multiple variable declarations without initialization are ok.
Lines containing multiple variable declarations initialized to a single function
call returning a tuple with the same number of values is also ok.
.Pp
Initialization
.Sy should
be done at declaration time as appropriate.
.Sh SEE ALSO
.Xr style 9
.Sh HISTORY
This manual page is inspired from the same source as
.Xr style 9
manual page in
.Fx .
